Hi Stephen,
On 11 May 2016 at 10:52, Stephen Warren swarren@wwwdotorg.org wrote:
On 05/10/2016 08:25 PM, Simon Glass wrote:
Hi Stephen,
On 4 May 2016 at 12:42, Stephen Warren swarren@wwwdotorg.org wrote:
On 05/01/2016 01:27 PM, Simon Glass wrote:
Hi Stephen,
On 28 April 2016 at 17:08, Stephen Warren swarren@wwwdotorg.org wrote:
From: Stephen Warren swarren@nvidia.com
This will allow a driver's bind function to use the driver data. One example is the Tegra186 GPIO driver, which instantiates child devices for each of its GPIO ports, yet supports two different HW instances each with a different set of ports, and identified by the udevice_id .data field.
Signed-off-by: Stephen Warren swarren@nvidia.com
drivers/core/device.c | 7 ++++--- drivers/core/lists.c | 6 +++--- drivers/gpio/dwapb_gpio.c | 2 +- drivers/gpio/s5p_gpio.c | 2 +- drivers/gpio/sunxi_gpio.c | 2 +- drivers/gpio/tegra_gpio.c | 2 +- drivers/mtd/spi/sandbox.c | 2 +- drivers/net/mvpp2.c | 3 ++- drivers/pci/pci-uclass.c | 5 ++--- drivers/power/pmic/pmic-uclass.c | 2 +- drivers/usb/host/usb-uclass.c | 5 ++--- include/dm/device-internal.h | 5 +++-- 12 files changed, 22 insertions(+), 21 deletions(-)
I'm not sure this extra parameter carries its weight:
- most callers just pass 0
The same is true of the existing platdata field in many cases.
Yes, but platdata is defined to be needed by bind(), whereas driver_data is supposed to be used in probe() to find out which device tree compatible string matched.
This seems to conflict with the documentation in include/dm/device.h; it claims that platdata is created by calling ofdata_to_platdata() just before calling probe(), at least for the DT case (for the case where U_BOOT_DEVICE is used, the platdata is available right from the start).
Exactly. That isn't a conflict. It's just that with DT the platform data is provided by ofdata_to_platdata() whereas without it (the degenerate case) it must be provided before bind().
I couldn't find anywhere in the documentation that states when driver_data is supposed to be used; could you point me at it so I can read it?
No, but we should add something. See device.h:
* @of_offset: Device tree node offset for this device (- for none) * @driver_data: Driver data word for the entry that matched this device with * its driver
It is related to DT, nothing else.
Remember that the device tree
properties are not looked at during bind(), only later. So it makes sense to include platdata in the device_bind() call, but not driver_data.
Hmm, drivers/gpio/tegra_gpio.c:gpio_tegra_bind() uses DT (which you wrote or at least converted it to DM and chose where to put the DT accesses), and you very recently reviewed and applied "video: tegra: refuse to bind to disabled dcs" which modified drivers/video/tegra.c:tegra_lcd_bind() to use DT.
Re GPIO, this is because on tegra this information is not present in the DT - it uses the 'interrupts' property to figure out the number of GPIO banks. It does not involve using driverdata.
The video thing is checking for a disabled device, something that is already done in dm_scan_fdt_node().
Admittedly I do now see the following in doc/driver-model/README.txt:
The device's bind() method is permitted to perform simple actions, but should not scan the device tree node, not initialise hardware, nor set up structures or allocate memory. All of these tasks should be left for the probe() method.
... but then I wonder why that rule was enforced for the patch in this thread, but not in the other cases?
This inconsistency in review is extremely frustrating to me.
See above. There are always grey areas, but the two you cite don't involve core DM changes.
- the field is supposed to be set up by device tree and probing tables,
not code
While the existence of this new parameter does allow arbitrary code to set the parameter, this patch only actually sets the parameter in the case where DT and probing tables have determined that value.
I don't think so. That value is set in lists_bind_fdt().
Sure, but that function is only used from 3 places, and explicitly accepts a parameter to indicate which DT node to instantiate a device for. It won't work unless a valid DT node is passed to it, and therefore can only work for DT-based probing.
I wonder if you could set it yourself after calling device_bind()?
The Tegra186 GPIO driver explicitly needs to use the data inside the driver's bind() function in order to know how many child devices to instantiate. Setting the value after calling device_bind() (which the core DM code already does) is too late.
For reference, you can see the exact code at: http://lists.denx.de/pipermail/u-boot/2016-April/252238.html "gpio: add Tegra186 GPIO driver"
Search for "tegra186_gpio_bind" and look at the assignment to, and use of, ctlr_data.
I had also quoted that part of the code in my previous email.
- bind() methods should not care about the driver data (they are not
allowed to touch hardware), so setting it later is fine
Not touching HW is fine, but the driver data can still feed into purely SW decisions that bind makes. More details below.
- you can already pass platform data to the driver which is the
preferred communication method from a parent to its children
I don't believe this is possible for devices instantiated from DT is it? In that case, platform data is always NULL:
That's right. For DT the paltform data is set up in the ofdata_to_platdata() method. Since you are using DT, you should follow that convention.
This is the opposite of what you said above, which was that platdata is for bind().
I'm really not sure what you are saying here. It seems quite straightforward to me:
- For the DT case (which is normal), the device tree data is used by ofdata_to_platdata() to create the platdata. Before that there is no platdata. The driver_data indicates which compatible string was matched - For the non-DT case (abnormal) it is provided by U_BOOT_DEVICE() and available before bind()
int lists_bind_fdt(struct udevice *parent, const void *blob, int offset,
()>>> struct udevice **devp)
... ret = device_bind(parent, entry, name, NULL, id->data, offset, &dev);
(That quoted code is with this patch applied, and the NULL value is the platform data parameter.)
Also it's not clear from your Tegra 186 GPIO patch where you are using this.
Here's the relevant part from the Tegra186 GPIO driver patch I posted:
+static int tegra186_gpio_bind(struct udevice *parent) +{
struct tegra186_gpio_platdata *parent_plat = parent->platdata;struct tegra186_gpio_ctlr_data *ctlr_data =(struct tegra186_gpio_ctlr_data *)parent->driver_data;...
/* If this is a child device, there is nothing to do here */if (parent_plat)return 0;...
for (port = 0; port < ctlr_data->port_count; port++) {...
plat->name = ctlr_data->ports[port].name;plat->regs = &(regs[ctlr_data->ports[port].offset / 4]);The data is used to determine how many child devices (one per port) to create, and the name and register offset of each one. This is modelled after the logic in the previous Tegra GPIO driver that you wrote, with the unfortunate modification that the register layout is more "interesting" on Tegra186, and so we can't determine the number of and parameters for the child devices purely algorithmically, since the register layout is decidedly non-linear.
OK I see. This feels like something that your device tree should describe.
DT generally describes the presence of HW blocks, not the internal details of those HW blocks, since that is a fixed facet of the hardware design and can be statically derived from the value of the compatible property.
Equally, I'm not sure how describing the details of the HW differences in DT would help. The details need to be known by the driver's bind() function, which you and the U-Boot documentation both state isn't allowed to access DT.
It would help because each bank would have a separate node, so you wouldn't need any of this logic.
Failing that, how about a hard-coded table of information in the source code? You can look through the table and create the appropriate child devices.
That is EXACTLY what the code is doing. The only issue is that the driver supports two different compatible properties and needs to know which one was found in DT in order to use the right table. That's what driver_data is; the .data value from the udevice_id/of_match table.
I suppose an alternative would be to create separate U_BOOT_DRIVER()s for each compatible value with different register layout, and then have the bind() for each of those call into some common implementation with a hard-coded parameter. Still, it seems like the usage in the current code is exactly what udevice_id.data is for; to avoid having to implement separate functions that do that.
Yes, but you should use different compatible strings for the nodes.
That's EXACTLY what the code does. However, there is currently no way for bind() to find out which entry in the udevice_id table matched, since the DM core currently sets driver_data after calling bind() rather than before.
OK I see.
As I understand it, you only have a single node, so re-purposing this does not seem right to me.
I must not understand what you're conveying by "single node" here. To quote the example from the Tegra186 GPIO DT binding documentation, here is what the DT looks like:
gpio@2200000 { compatible = "nvidia,tegra186-gpio"; reg-names = "security", "gpio"; reg = <0x0 0x2200000 0x0 0x10000>, <0x0 0x2210000 0x0 0x10000>; interrupts = <0 47 IRQ_TYPE_LEVEL_HIGH>, <0 50 IRQ_TYPE_LEVEL_HIGH>, <0 53 IRQ_TYPE_LEVEL_HIGH>, <0 56 IRQ_TYPE_LEVEL_HIGH>, <0 59 IRQ_TYPE_LEVEL_HIGH>, <0 180 IRQ_TYPE_LEVEL_HIGH>; gpio-controller; #gpio-cells = <2>; interrupt-controller; #interrupt-cells = <2>; }; gpio@c2f0000 { compatible = "nvidia,tegra186-gpio-aon"; reg-names = "security", "gpio"; reg = <0x0 0xc2f0000 0x0 0x1000>, <0x0 0xc2f1000 0x0 0x1000>; interrupts = <0 60 IRQ_TYPE_LEVEL_HIGH>; gpio-controller; #gpio-cells = <2>; interrupt-controller; #interrupt-cells = <2>; };Those two HW blocks are roughly but not exactly the same HW. Hence, there are two compatible values. The two HW blocks are similar enough to be handled by a single driver though, and hence the udevice_id table has two entries:
static const struct udevice_id tegra186_gpio_ids[] = { { .compatible = "nvidia,tegra186-gpio", .data = (ulong)&tegra186_gpio_main_data, }, { .compatible = "nvidia,tegra186-gpio-aon", .data = (ulong)&tegra186_gpio_aon_data, }, { } };
The .data value there provides all necessary information for the driver to handle both HW block designs.
All I need is to be able to access the ".data" from that table in bind(), whereas the DM core currently doesn't allow that.
OK
Perhaps the creation of the child devices could happen in probe() rather than bind()? I imagine there's some reason this wouldn't work (such as this causing the devices to be created too late to be referenced by other drivers?) or you would have done this in the existing Tegra GPIO driver.
Best not - it is good to have the devices known on start-up. Let me know if the above solution doesn't work.
I must admit, I didn't see any solution offered in your email.
If the child devices must be created in bind(), which I do agree makes sense, then bind() must be able to determine which udevice_id table entry is related to the device being bound. Is there another way to do that besides using the driver_data from the udevice_id table? I suppose I could make bind() go read the compatible property from the DT node for the device, and manually search through the udevice_id table and find the matching entry. However, that would be duplicating work the DM core has already done, and exposes by setting the device's driver_data right after calling the driver's bind(), so doesn't make sense to me.
I was suggesting passing the platform data pointer to device_bind(), but actually it doesn't help here as it is the parent device that needs it.
This is a hard case. I think the least worst alternative is to add a new device_bind_with_driver_data() function which can be called only within driver model (from lists_bind_fdt() and I suppose device_bind()). The existing device_bind() function signature can then be left alone. Would that suit?
If so, can you please do a core DM patch and update the README to explain this usage?
Regards, Simon